JP4942540B2 - Near-infrared absorbing film and optical filter for plasma display panel using the same - Google Patents

Description

  The present invention relates to an optical film in which a pressure-sensitive adhesive layer having near infrared absorption ability is provided on a transparent substrate, and an application thereof. More specifically, a near-infrared absorbing film provided with an adhesive layer formed by coating an adhesive containing a near-infrared absorbing dye and a copolymer on a transparent substrate, and a plasma display panel (hereinafter referred to as PDP) using the same. This relates to an optical filter.

  The principle of PDP is that a voltage is applied to a rare gas (neon, xenon) enclosed in a cell sandwiched between two glass substrates, and ultraviolet light emitted from the rare gas in a plasma state excites the phosphor coated on the cell wall. Thus, visible light necessary for the image is generated. From such a PDP, electromagnetic waves that are harmful to the human body or electrical appliances at the same time as visible light, for example, near infrared rays having a wavelength of 800 nm to 1100 nm that are harmful to electrical appliances, orange light rays having a wavelength near 595 nm that lowers the color purity of red light (hereinafter referred to as “red light”) , And so on), an optical filter that shields (cuts) harmful electromagnetic waves other than visible light necessary for an image is required.

  In particular, near-infrared light may cause malfunctions in remote controllers that use near-infrared light of electrical equipment and communication devices that use near-infrared light such as personal computers and cordless phones. It is essential to install an optical filter having a function of blocking.

  As a filter for blocking near infrared rays, a method using an optical filter having a near infrared ray absorbing film as a constituent element has been proposed. This near-infrared absorbing film is produced, for example, by coating a binder resin containing a near-infrared absorbing pigment on a transparent film such as polyethylene terephthalate (PET). The near-infrared absorbing dye used has a maximum absorption wavelength in the range of 800 nm to 1100 nm, for example, a diimonium dye, a cyanine dye, an indocyanine dye, a polymethine dye, a squarylium dye, a phthalocyanine dye, a dithiol complex dye Dyes and azo dyes are widely used. Among these, diimonium dyes having a relatively wide absorption wavelength region in the near infrared region are preferably used alone or in combination with other near infrared absorbing dyes based on this.

However, when preparing an optical filter having the ability to absorb and block electromagnetic waves as described above in addition to the near-infrared absorbing ability, a transparent substrate such as glass is provided through an adhesive layer separately provided with a film having near-infrared absorbing ability In the method of laminating, the manufacturing process increases and the production efficiency decreases. Therefore, an attempt is made to contain a near infrared absorbing dye in the adhesive layer itself, thereby shortening the optical filter manufacturing process and providing near infrared absorbing ability between any layers constituting the optical filter. Therefore, it can be expected that the efficiency of manufacturing the optical filter is improved. For example, Patent Document 1 describes a near-infrared absorbing film in which a near-infrared absorbing pigment is contained in an acrylic resin adhesive.
However, when a near-infrared absorbing dye such as a diimonium dye is contained in the adhesive layer, there is a problem that the heat stability and the heat-and-moisture stability are deteriorated, and the unstable near-infrared absorbing dye is stabilized in the adhesive layer. Various studies have been conducted. For example, in Patent Document 2, it is proposed to use a silicon-based adhesive as the adhesive material, but the silicon-based adhesive is not sufficiently compatible with the infrared absorbing dye, and its handling, particularly the adhesive layer forming step, There is a difficulty that it is troublesome.
Japanese Patent No. 3621322 JP 2005-62506 A

  A near-infrared-absorbing dye is contained in a layer provided by applying an adhesive (hereinafter referred to as an adhesive layer), and a near-infrared-absorbing film that has excellent heat resistance and heat-and-moisture resistance and maintains good optical properties is prepared. It is an object of the present invention to provide an optical filter for PDP using this.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors include a specific (meth) acrylic acid alkyl ester copolymer as a pressure-sensitive adhesive when forming a pressure-sensitive adhesive layer containing a near-infrared absorbing dye. The inventors have found that the above-mentioned problems can be solved by using what to do, and have completed the present invention.

That is, the present invention is (1) formed on one surface of a transparent substrate by a pressure-sensitive adhesive containing a copolymer having a near-infrared absorbing dye and a (meth) acrylic acid fluorinated alkyl ester as essential constituent monomers. A near-infrared absorbing film provided with an adhesive layer,
(2) The copolymer is a copolymer having (meth) acrylic acid (C3-C10) alkyl ester as an essential constituent monomer in addition to (meth) acrylic acid fluorinated alkyl ester Near-infrared absorbing film,
(3) The near-infrared absorbing film according to (1) or (2), wherein the (meth) acrylic acid fluorinated alkyl ester is tetrafluoropropyl acrylate, hexafluoropropyl acrylate, octafluoropentyl acrylate or heptadecafluorodecyl acrylate. ,
(4) The near-infrared absorbing film according to any one of (1) to (3), wherein the near-infrared absorbing dye is a diimonium-based dye represented by the following formula (1):

(In formula (1), R _{1 to} R ₈ each independently represents an aliphatic hydrocarbon residue optionally having a hydrogen atom or a substituent, and X represents a monovalent anion residue)
(5) The near-infrared absorbing film according to any one of (1) to (4), wherein the pressure-sensitive adhesive contains a crosslinking agent,
(6) An optical filter for a plasma display panel comprising the near-infrared absorbing film according to any one of (1) to (5) and a film having an electromagnetic wave shielding function and / or a film having a low reflection function,
About.

The near-infrared absorbing film provided with the pressure-sensitive adhesive layer according to the present invention has good near-infrared absorption performance and optical characteristics, excellent heat resistance and stability, and further has a pressure-sensitive adhesive layer so that it can be easily used with other functional films. The optical filter for PDP and the like can be prepared very easily.

The present invention will be described in detail.
The near-infrared absorbing film of the present invention comprises an acrylic resin adhesive layer on one side of a transparent substrate, and the adhesive forming the adhesive layer uses (meth) acrylic acid fluorinated alkyl ester as a monomer component. A near-infrared absorbing film comprising an acrylic acid-containing copolymer as a main component, and the adhesive layer containing a near-infrared absorbing dye such as a diimonium dye represented by the formula (1). .

The pressure-sensitive adhesive used in the present invention contains a copolymer having (meth) acrylic acid fluorinated alkyl ester as an essential constituent monomer as a main constituent component. In a preferred embodiment, the copolymer is a copolymer having (meth) acrylic acid fluorinated alkyl ester and (meth) acrylic acid (C3 to C10) alkyl ester as essential constituent monomers.
Specific examples of the (meth) acrylic acid fluorinated alkyl ester include, for example, trifluoroethyl acrylate, trifluoroethyl methacrylate, tetrafluoropropyl acrylate, tetrafluoropropyl methacrylate, hexafluoropropyl acrylate, hexafluoropropyl methacrylate, octafluoro Examples include pentyl acrylate, octafluoropentyl methacrylate, heptadecafluorodecyl acrylate, heptadecafluorodecyl methacrylate, and the like. Among these, it is preferable to select from the group consisting of tetrafluoropropyl acrylate, hexafluoropropyl acrylate, octafluoropentyl acrylate or heptadecafluorodecyl acrylate.

  Specific examples of (meth) acrylic acid (C3 to C10) alkyl esters include, for example, (meth) acrylic acid n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl. , N-pentyl, iso-pentyl, n-hexyl, 2-ethylbutyl, cyclohexyl, 2-ethylhexyl, n-octyl, n-decyl, benzyl, and the like. Among these, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, n-hexyl, 2-ethylbutyl, cyclohexyl or 2-ethylhexyl ester of acrylic acid is preferable. These esters may be used in combination of two or more as required.

Further, other monomers that can be used in addition to the above-mentioned two systems of monomers used for synthesizing the copolymer will be described.
The (meth) acrylic acid-based monomer having a functional group is utilized as a reaction point in the case of using a crosslinking agent, improving the adhesiveness by the crosslinking reaction, and improving the cohesion and heat resistance by controlling the glass transition temperature of the copolymer. Improvements can be expected. Specific examples of the (meth) acrylic acid monomer having a functional group include monomers having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid or fumaric acid, hydroxyethyl (meth) acrylate, Hydroxyl group-containing monomers such as hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, methoxyethyl (meth) acrylate, methoxybutyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate or (meth) Examples include monomers having an ether group such as phenoxyethyl acrylate, monomers having an amide group such as acrylamide, N, N-dimethylacrylamide or morpholylacrylamide, and monomers having an epoxy group such as glycidyl methacrylate. .
The proportion of these other monomers used is preferably from 0.5 to 10% by weight, more preferably from 2 to 6% by weight, based on the total monomer weight constituting the copolymer.

  In the copolymer of the present invention, the ratio of the (meth) acrylic acid fluorinated alkyl ester to the (meth) acrylic acid (C3 to C10) alkyl ester is 1 to 20, preferably 1 to 20, with respect to the former 1 by weight. 3-15. When the amount of (meth) acrylic acid (C3 to C10) alkyl ester used is less than 1, the adhesive strength may be reduced, while the amount of (meth) acrylic acid (C3 to C10) alkyl ester used is 20 or more. When it increases, there exists a possibility that the heat-resistant stability and heat-and-moisture-resistant stability of the near-infrared absorption pigment | dye contained in the adhesion layer may fall. When the above-mentioned other monomers are added to the copolymer in addition to the two esters, as described above, the amount used is 0.5 to 10% by weight based on the total monomer weight constituting the copolymer. Is preferable, and 2 to 6% by weight is more preferable.

  In the synthesis of the copolymer which is a main component of the pressure-sensitive adhesive in the present invention, any polymerization method known per se such as solution polymerization, suspension polymerization, bulk polymerization and the like can be applied.

  When performing polymerization, it is preferable to use a radical polymerization initiator. Specific examples of radical polymerization initiators that can be used include benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, azobisisobutyronitrile, azobiscyclohexanecarbox. Nitrile, potassium persulfate, ammonium persulfate and the like can be mentioned, and any of those that can be used for ordinary radical polymerization can be used. The amount of the polymerization initiator used is not particularly limited, but is preferably in the range of 0.01 to 1.0% by weight based on the total weight of the monomer components.

  The polymerization temperature is preferably in the range of 0 to 200 ° C., particularly in the range of 50 to 100 ° C. from the viewpoints of polymerization rate, reaction control, molecular weight and the like. The polymerization time depends on the polymerization temperature, is in the range of 1 to 48 hours, and is preferably in the range of 3 to 12 hours. The copolymer used in the present invention preferably has a weight average molecular weight of 100,000 or more, particularly 6 million to 2 million, from the viewpoints of heat resistance and adhesive properties. (Hereinafter, the copolymer thus obtained is also referred to as an acrylic acid copolymer.)

The near-infrared absorbing dye used in the present invention is not particularly limited as long as it has a maximum absorption wavelength at 800 nm to 1100 nm. Examples of the near-infrared absorbing dye that can be used include diimonium dyes and nitroso compounds. And metal salts thereof, cyanine dyes, indocyanine dyes, polymethine dyes, squarylium dyes, phthalocyanine dyes, naphthalocyanine dyes, triarylmethane dyes, thiol nickel complex compounds, dithiol complex dyes, naphthoquinone dyes Examples thereof include dyes, anthraquinone dyes, and azo dyes.
Among these, a diimonium dye having a relatively wide absorption wavelength region in the near infrared region is preferably used. The diimonium dye that is particularly preferably used in the present invention is represented by the formula (1). R _{1 to} R ₈ in the formula (1) each independently represent a hydrogen atom or an aliphatic hydrocarbon residue which may have a substituent. Here, the aliphatic hydrocarbon residue means a group obtained by removing one hydrogen atom from a saturated and unsaturated linear, branched or cyclic aliphatic hydrocarbon. 1-12 are preferable, and C3-C8 is more preferable from the surface of the solubility with respect to an organic solvent, and heat stability.

Specific examples of saturated linear and branched aliphatic hydrocarbon residues include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl. Group, tert-butyl group, n-pentyl group, iso-pentyl group, tert-pentyl group, n-hexyl group, iso-hexyl group, n-octyl group, iso-octyl group, decyl group or dodecyl group. It is done. Among these, preferred are n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, n-pentyl group or neopentyl group.
The aliphatic hydrocarbon residue is an aryl group (eg, phenyl group, benzyl group, phenylethyl group, etc.), a halogen atom (eg, fluorine, chlorine, bromine), a hydroxy group, an alkoxy group (eg, methoxy group, ethoxy group). , Propoxy group, etc.), alkoxyalkyl group (eg, methoxyethyl group), aryloxy group, acyloxy group (eg, acetyloxy group, butyryloxy group, benzoyloxy group), N, N-dialkylamino group, cyano group, sulfo group It may have a substituent such as an alkyl group (eg, sulfomethyl group), a carboxyl group, or an alkoxycarbonyl group (eg, methoxycarbonyl group).

  Preferable specific examples of the aliphatic hydrocarbon residue having a substituent include a cyanomethyl group, 2-cyanoethyl group, 2- or 3-cyanopropyl group, 2-, 3- or 4-cyanobutyl group, 2-, 3- , 4- or 5-cyanopentyl group and other cyano-substituted alkyl groups, methoxyethyl group, ethoxyethyl group, 3-methoxypropyl group, 3-ethoxypropyl group, 4-methoxybutyl group, 4-ethoxybutyl group, 5- Alkoxy-substituted alkyl groups such as methoxypentyl group and 5-ethoxypentyl group, monofluoromethyl group, trifluoromethyl group, trifluoroethyl group, tetrafluoroethyl group, pentafluoroethyl group, heptafluoropropyl group, perfluorobutyl group, Such as perfluoropentyl, perfluorohexyl or perfluorooctyl Examples thereof include a nitrogen-substituted alkyl group.

  Specific examples of unsaturated linear and branched aliphatic hydrocarbon residues include vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, pentenyl group, hexenyl group, isohexenyl group or octenyl group. Etc., and may have a substituent such as a halogen atom, a hydroxy group, an alkoxy group or a carboxy group.

  Specific examples of the cyclic aliphatic hydrocarbon residue include a cyclopentyl group, a cyclohexyl group, and a cyclohexenyl group, which may have the above substituents.

These groups can exist independently, for example, R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ and R ₇ and R ₈ are different combinations of groups. May be. For example, one amino group substituted with an unsubstituted linear alkyl group and an unsubstituted branched alkyl group, or one substituted with an unsubstituted linear alkyl group and a cyano substituted alkyl group may be used. It is preferable that at least one of R _{1 to} R ₈ is a branched alkyl group, and it is more preferable that R _{1 to} R ₈ are all alkyl groups branched at the terminal. Examples of the alkyl group in which R _{1 to} R ₈ are all branched at the terminal include an iso-propyl group, an iso-butyl group, an iso-pentyl group, an iso-hexyl group, and the like, and R _{1 to} R ₈ Are all preferably iso-butyl groups.

  The X anion in the formula (1) is a monovalent anion, and examples thereof include an inorganic anion, an organic acid anion, and an organic metal anion.

  Specific examples of inorganic anions include, for example, halogen ions such as fluorine ion, chlorine ion, bromine ion or iodine ion, thiocyanate ion, hexafluoroantimonate ion, perchlorate ion, periodate ion, nitrate ion, tetrafluoro ion. Borate ion, hexafluorophosphate ion, molybdate ion, tungstate ion, titanate ion, vanadate ion, phosphate ion, borate ion, tetrafluorotantalate ion or tetrafluoroniobate ion, etc. Preferred are strong acid anions, and preferred are perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion or hexafluoroantimonate ion.

  Specific examples of organic acid and organic metal anions include organic carboxylate ions such as acetate ion, lactate ion, trifluoroacetate ion, propionate ion, benzoate ion, oxalate ion, succinate ion or stearate ion. Methane sulfonate ion, toluene sulfonate ion, naphthalene monosulfonate ion, chlorobenzene sulfonate ion, nitrobenzene sulfonate ion, dodecylbenzene sulfonate ion, benzene sulfonate ion, ethane sulfonate ion or trifluoromethane sulfonate ion, etc. Organic sulfonate ion, tetraphenylborate ion, organic borate ion such as butyltriphenylborate ion, bistrifluoromethanesulfonylimido ion, tristrifluoromethanesulfo Fluorine-containing organic acid ion such as Rumechido acid ion. Preferable examples include bistrifluoromethanesulfonylimido ion and tristrifluoromethanesulfonylmethide ion which are strong acid anions.

  Of these anions, trifluoromethanesulfonylimido ion and tristrifluoromethanesulfonylmethide ion are particularly preferred.

  The diimonium dye used in the present invention may be used alone, but for the purpose of extending the desired near-infrared absorption wavelength range or adjusting the absorption ratio, one or more other near-infrared absorptions. Examples of other near infrared absorbing compounds may include diimonium dyes other than the present diimonium dyes, nitroso compounds and their metal salts, cyanine dyes, squarylium dyes, thiol nickel complex compounds Phthalocyanine dyes, naphthalocyanine dyes, triarylmethane dyes, naphthoquinone dyes, anthraquinone dyes, and the like. When using a dye other than the diimonium dye, the ratio of the diimonium dye in the all infrared absorbing dye is preferably 50% by weight or more.

The acrylic acid copolymer can be subjected to crosslinking treatment by blending a crosslinking agent (curing agent) with the pressure-sensitive adhesive. Specific examples of the crosslinking agent that can be used include aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylolpropane adduct of hexamethylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, or trimethylol propane of tolylene diisocyanate. Polyisocyanates such as aromatic diisocyanates such as adducts, melamine compounds such as trimethylol melamine, polyamines such as hexamethylenediamine or triethylamine, epoxy compounds such as polyethylene glycol diglycidyl ether or trimethylolpropane triglycidyl ether, aluminum A metal chelate compound such as acetylacetone or a metal salt such as aluminum chloride is used. You may use these in mixture of 2 or more types.
The amount of the crosslinking agent is 0.005 to 5 parts by weight, preferably 0.01 to 3 parts by weight, per 100 parts by weight of the acrylic acid copolymer.

In addition to the above-mentioned components, the pressure-sensitive adhesive in the present invention is appropriately selected from polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polycarbonate resins, natural or synthetic rubber resins, silicon resins, and the like as necessary. Can be blended.
In order to improve the durability of the pressure-sensitive adhesive layer containing a near-infrared absorbing dye, an antioxidant or an ultraviolet absorber can be added. Examples of the antioxidant include phenol-based, amine-based, hindered phenol-based, Examples of hindered amine-based, sulfur-based, phosphoric acid-based, phosphorous acid-based, or metal complex-based materials include ultraviolet absorbers such as benzophenone-based and benzotriazole-based materials. Furthermore, a color tone correction dye, a neon light absorption dye, a leveling agent, an antistatic agent, and the like having a maximum absorption wavelength in the range of 300 to 800 nm may be contained as long as the effects of the present invention are not impaired.

  The pressure-sensitive adhesive used in the present invention contains the above-described components, for example, 100 parts by weight of the acrylic acid-based copolymer, 0.1 to 20 parts by weight of a near-infrared absorbing dye, other additives such as an ultraviolet absorber and a crosslinking agent. It is obtained by mixing and stirring at a ratio of 0 to 10 parts by weight. However, in consideration of the coating treatment to the transparent substrate, for example, 100 parts by weight of the acrylic acid copolymer, 0.1 to 20 parts by weight of near infrared absorbing dye, UV absorber, cross-linking agent, and the like. It is preferable to obtain a pressure-sensitive adhesive in which 0 to 10 parts by weight of the additive is dissolved or dispersed in a solvent, and after performing filtration treatment or the like as necessary, to prepare a coating liquid. In this case, it is preferable to adjust so that the content of the pressure-sensitive adhesive in the coating solution is 10 to 30% by weight, preferably 15 to 25%.

  The near-infrared absorbing film of the present invention can be produced by coating the above-described coating solution on the transparent support film described below and drying it. The thickness of the pressure-sensitive adhesive layer containing the near-infrared absorbing dye and other additives is usually 1 to 50 μm, preferably 10 to 30 μm, and the pressure-sensitive adhesive layer is fixed by drying at 80 to 140 ° C. Is done.

  Further, an adhesive layer containing a near-infrared absorbing dye and other additives is provided on a release (release) film such as a polyethylene terephthalate film in the same manner as described above, and then the functionality of the functional film described later is provided. A method of transferring the pressure-sensitive adhesive layer by adhering to the surface opposite to the surface on which the layer is provided can also be employed.

  Examples of the solvent include aliphatic hydrocarbons such as n-hexane and n-heptane, aromatic hydrocarbons such as toluene and xylene, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclopentanone, methanol, Alcohols such as ethanol and i-propyl alcohol, ethers such as tetrahydrofuran and ethylene glycol monomethyl ether, esters such as ethyl acetate and butyl acetate, aliphatic halogens such as chloroform, methylene chloride and dichloroethylene, N, N-dimethyl Examples include amides such as formamide and N, N-dimethylacetamide. These organic solvents may be used alone, or may be appropriately mixed and used as necessary.

  The coating liquid is applied by a flow coating method, a spray coating method, a wire bar coating method, a blade coating method, a gravure coating method, a gravure reverse coating method, a roller coating method, a slit die coating method or a comma coater method. Can be used.

Examples of the material for the transparent support film used in the present invention include polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polycarbonates (PC), triacetates, polyacrylates, and polymethacrylates (PMMA). ), Polyolefins such as polyethylene and polypropylene, polystyrenes, celluloses, polyurethanes, polyvinyl chlorides, and the like, which can be appropriately selected and used, and preferably PET, PC, and PMMA are used.
The thickness of the support film is preferably in the range of 10 to 500 μm because the workability is good. Further, the surface of the support film can be coated with a corona discharge treatment, a plasma treatment, a glow discharge treatment, an anchor coating agent, a primer or the like in order to improve the adhesion with the coating film.
The transparent support film is more preferably a film having a single function or a plurality of functions such as anti-reflection, anti-glare / anti-reflection, antistatic, antifouling, electromagnetic wave shielding, and color tone adjustment. A rational production of the filter becomes possible.

  Although the near-infrared absorbing film of the present invention can be used alone as an optical film, in a preferred embodiment, two or more kinds of films having any functionality other than the near-infrared absorbing film of the present invention are laminated. And used as an optical filter. Here, as a film having arbitrary functionality, for example, from a display device such as an antireflection film or an antiglare film for preventing background reflection on the display unit and at the same time improving the contrast of the display image, PDP, etc. Electromagnetic wave shielding film for cutting emitted electromagnetic wave, film for cutting neon light, hard coat layer giving scratch resistance or film having antifouling layer for preventing dirt on outermost surface, each layer Examples thereof include a pressure-sensitive adhesive or an adhesive film for laminating.

Next, examples of the functional film will be described below, but the functional film is not limited thereto.
The antireflection film reduces reflected light by causing surface reflected light and interface reflected light to interfere with each other. A hard coat layer between a film or a transparent support film and a low refractive index layer provided with a low refractive index layer obtained by coating a surface of a transparent support film such as PET with a low refractive index agent such as magnesium fluoride or silica together with a binder resin For example, the film is provided with a high refractive index layer coated with a high refractive agent such as titanium oxide, zinc oxide, zirconia, etc., and is controlled so as to cancel reflected light from each layer, thereby improving visibility. Anti-glare and anti-reflective film is made by dispersing fine particles such as polystyrene resin and acrylic resin in the high refractive index layer and other layers of the anti-reflective film, and diffused reflection of external light to further improve visibility. It is a improved film.

  The electromagnetic shielding film has a mesh type in which ultrafine wires of metal such as copper are held on a transparent support film in a geometric pattern like a mesh, and an ultrathin metal film is used as a transparent support film within the range of visible light transmission There is a thin film type that is held, and since the thin film type generally does not reflect and transmit near infrared rays, a near infrared ray absorbing film is not required, so the electromagnetic wave shielding film laminated on the near infrared ray absorbing film of the present invention is of the mesh type Can be used.

In PDP, neon light having a wavelength of 550 to 620 nm derived from Ne gas generated at the time of applied voltage needs to be cut to some extent in front of the display in order to reduce the color purity of red light. A neon light absorption filter held in the above is used. Examples of the neon light absorbing compound include azaporphyrin, cyanine, squarylium, azomethine, xanthene, and azo compounds.
In addition, the method of obtaining the layer which can absorb a near infrared ray and a neon light simultaneously can be employ | adopted by containing the compound which has a neon light absorption capability in the above-mentioned adhesive layer which has a near infrared absorption capability.

  The optical filter of the present invention is obtained by sequentially laminating the above-mentioned films having other functions such as an electromagnetic wave shielding function and a reduced reflection function on the transparent base material with the near infrared ray absorbing film of the present invention as the minimum constituent element. The optical filter of the present invention may be bonded to a glass plate or a plastic plate in advance and attached to the front surface of the PDP, or may be directly bonded to the front surface of the PDP.

  The near-infrared absorbing film of the present invention has a simple manufacturing method and excellent near-infrared absorptivity over time. At the same time, the near-infrared absorbing film has an adhesive ability to glass, PET film, polycarbonate and the like used as a substrate for optical functional films. Are better. An optical filter obtained by laminating another functional film on the near infrared absorbing film gives an excellent near infrared absorbing effect in combination with other functions as an optical filter for PDP.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the examples, “parts” represents parts by weight and “%” represents percent by weight, unless otherwise specified.

Reference Example 1 (Synthesis of Copolymer 1)
In a 1 l flask equipped with a stirrer, a condenser, a temperature sensor, and a nitrogen introduction tube, 80 parts of butyl acrylate, 16 parts of octafluoropentyl acrylate, 4 parts of acrylic acid, and 100 parts of ethyl acetate were stirred and dissolved. After introducing nitrogen to bring the oxygen concentration in the gas phase to 0.1% or less, the mixture was heated to 80 ° C., 0.03 part of benzoyl peroxide as a polymerization initiator dissolved in a small amount of ethyl acetate was added, and 85 ° C. The copolymer of butyl acrylate, octafluoropentyl acrylate, and acrylic acid was obtained by heating and polymerizing for 7 hours. Methyl ethyl ketone was added to this copolymer to obtain a resin solution dissolved so as to have a copolymer concentration of 25%. The weight average molecular weight by GPC was 1.3 million.

Reference Example 2 (Synthesis of Copolymer 2)
In the same manner as in Reference Example 1 except that 88 parts of butyl acrylate, 8 parts of heptadecafluorodecyl acrylate and 4 parts of acrylic acid are used in Reference Example 1, butyl acrylate, heptadecafluorodecyl acrylate, acrylic acid The copolymer of was obtained. Methyl ethyl ketone was added to this copolymer to obtain a resin solution dissolved so as to have a copolymer concentration of 25%. The weight average molecular weight by GPC was 1.1 million.

Reference Example 3 (Synthesis of comparative copolymer)
In Reference Example 1, a copolymer of butyl acrylate and acrylic acid was obtained in the same manner as in Reference Example 1, except that 96 parts of butyl acrylate and 4 parts of acrylic acid were used. Methyl ethyl ketone was added to this copolymer to obtain a resin solution dissolved so as to have a copolymer concentration of 25%. The weight average molecular weight by GPC was 1,500,000.

Example 1 (Preparation of a near-infrared absorbing film)
A coating solution prepared by mixing and dissolving the raw materials shown in Table 1 so as to be uniform is coated on PET • 3811 (trade name, exfoliated PET film, manufactured by Lintec) with a comma coater and dried at a coating speed of 0.8 m / min. At a temperature of 110 ° C., the pressure-sensitive adhesive layer was coated to a thickness of 18 μm to form a pressure-sensitive adhesive layer, and through this pressure-sensitive adhesive layer, KAYACOAT ARS-D511 (trade name, anti-reflection film, Nippon Kayaku) The near-infrared absorbing film of the present invention having a low reflection property was obtained by pasting it on the opposite surface of the reduced reflection surface.

Table 1
Raw material Amount used Adhesive (Copolymer 1 of Reference Example 1) 120.0 parts Near-infrared absorbing dye (diimonium dye, R _{1 to} R ₈ in formula (1) are a mixture of iso-butyl and n-propyl, X is tristrifluoromethanesulfonylmethideate ion residue) 1.5 parts UV absorber (trade name Tinuvin 109; manufactured by Ciba Geigy) 1.0 part hardener (trade name M12ATY; manufactured by Nippon Kayaku Co., Ltd.) 0.37 parts cured Agent (trade name L45EY; manufactured by Nippon Kayaku Co., Ltd.) 0.45 parts methyl ethyl ketone 76.7 parts (註) trade name Tinuvin 109; benzotriazole compound, trade name M12ATY; metal chelate compound, trade name L45EY; isocyanate compound,

(Production of optical filter for PDP)
On the opposite surface of the protective film of ES-1534U (HCD-42-02) (trade name, electromagnetic wave shielding film, manufactured by Hitachi Chemical Co., Ltd.) having a protective film and an adhesive layer, the peel-off PET film of the infrared absorbing film is peeled off. It bonded through the adhesion layer and obtained the optical filter for PDP. This optical filter peels off the protective film, and can be applied directly to the front of the PDP module, or attached to a transparent plate such as a glass plate and mounted in front of the module. It was a thing.

Example 2 (Preparation of a near-infrared absorbing film)
A coating solution prepared by mixing and dissolving the raw materials shown in Table 2 uniformly is coated on PET • 3811 (trade name, exfoliated PET film, manufactured by Lintec) with a comma coater and dried at a coating speed of 0.8 m / min. At a temperature of 110 ° C., the pressure-sensitive adhesive layer was coated to a thickness of 18 μm to form a pressure-sensitive adhesive layer, and through this pressure-sensitive adhesive layer, KAYACOAT ARS-D511 (trade name, anti-reflection film, Nippon Kayaku) The near-infrared absorbing film of the present invention having a low reflection property was obtained by pasting it on the opposite surface of the reduced reflection surface.

Table 2
Raw material Amount used Adhesive (Copolymer 2 of Reference Example 2) 120.0 parts Near-infrared absorbing dye (diimonium dye, R _{1 to} R ₈ in formula (1) are a mixture of iso-butyl and n-propyl, X is tristrifluoromethanesulfonylmethideate ion residue) 1.5 parts UV absorber (trade name Tinuvin 109; manufactured by Ciba Geigy) 1.0 part hardener (trade name M12ATY; manufactured by Nippon Kayaku Co., Ltd.) 0.37 parts cured Agent (trade name L45EY; manufactured by Nippon Kayaku Co., Ltd.) 0.45 parts methyl ethyl ketone 76.7 parts (註) trade name Tinuvin 109; benzotriazole compound, trade name M12ATY; metal chelate compound, trade name L45EY; isocyanate compound,

(Production of optical filter for PDP)
On the opposite surface of the protective film of ES-1534U (HCD-42-02) (trade name, electromagnetic wave shielding film, manufactured by Hitachi Chemical Co., Ltd.) having a protective film and an adhesive layer, the peel-off PET film of the infrared absorbing film is peeled off. It bonded through the adhesion layer and obtained the optical filter for PDP. This optical filter can be applied directly to the front of the PDP module by peeling off the protective film, or it can be attached to a transparent plate such as a glass plate and attached to the front of the module. Met.

Comparative Example 1 (Preparation of near-infrared absorbing film)
In the composition shown in Table 1, a near-infrared absorbing film having reduced reflectivity was obtained in the same manner as in Example 1 except that the adhesive was changed to the comparative copolymer of Reference Example 3.

(Test method)
About the near-infrared absorbing films of Examples 1 and 2 and Comparative Example 1, luminous transmittance (Y /%) immediately after production (0 hour) and after heat resistance and moist heat resistance tests (500 hours), near infrared Changes in transmittance and haze at a region wavelength of 950 nm were measured. The heat resistance test was 80 ° C., the humidity and heat resistance test was 60 ° C., and the relative humidity was 90% in a constant temperature / humidity bath for 500 hours. The results of the durability test are shown in Tables 3 and 4.
In each table, luminous transmittance (Y /%), transmittance in the near infrared region wavelength 950 nm are measured with UV-3150 (trade name, spectrophotometer, manufactured by Shimadzu Corporation), and haze measurement is performed with TC. -HIIIDPK (trade name, haze meter, manufactured by Tokyo Denshoku) was used.

(Consideration of results)
As can be seen from the results in Tables 3 and 4, the near-infrared absorbing films of Example 1 and Example 2 have better luminous transmittance than those of the comparative examples, and there is little change after the durability test, especially haze. In addition, the change in transmittance at a wavelength of 950 nm was small and good.

Claims (6)

Near-infrared light comprising an adhesive layer formed of a pressure-sensitive adhesive containing a copolymer containing a near-infrared absorbing dye and a (meth) acrylic acid fluorinated alkyl ester as essential constituent monomers on one surface of a transparent substrate Absorption film. The near-infrared absorbing film according to claim 1, wherein the copolymer is a copolymer having an acrylic acid (C 3 to C 10) alkyl ester as an essential constituent monomer in addition to the (meth) acrylic acid fluorinated alkyl ester. The near-infrared absorbing film according to claim 1 or 2, wherein the (meth) acrylic acid fluorinated alkyl ester is tetrafluoropropyl acrylate, hexafluoropropyl acrylate, octafluoropentyl acrylate or heptadecafluorodecyl acrylate. The near-infrared absorbing film according to any one of claims 1 to 3, wherein the near-infrared absorbing dye is a diimonium-based dye represented by the following formula (1).

(In Formula (1), R _{1 to} R ₈ each independently represents an aliphatic hydrocarbon residue which may have a hydrogen atom or a substituent, and X represents a monovalent anion residue.) The near-infrared absorbing film according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive contains a crosslinking agent. An optical filter for a plasma display panel comprising the near-infrared absorbing film according to any one of claims 1 to 5, a film having an electromagnetic wave shielding function, and / or a film having a low reflection function as constituent elements.